| Direct-fired absorption chillers can often be modified to accept hot air
or exhaust from a gas turbine or engine. Performance is almost totally
dependent upon air temperature, For example, waste heat air temperatures °F
or higher offer performance similar to direct-fired absorption chillers
where every 13,000 Btu of heat recovered produces one ton of cooling. When
calculating heat recovery, remember to assume waste heat leaving the
absorption chiller at 375° to 400°F (this means the absorption chiller will
not reclaim all of the waste heat potential).
For exhaust gas heat recovery
Chilling capacity (tons) / 40,950 = m x (Tg - 375)
Heating capacity (Btuh) = m x (Tg - 375) x 0.257
where m = exhaust gas flow rate in pounds per hour
Tg = exhaust gas inlet temperature in °F
40,950 = cooling constant representing average gas specific heat,
interconnect efficiency, cooling COP and the conversion from Btuh to tons
0.257 = heating constant representing average gas specific heat and the
interconnect efficiency
375 = minimum temperature of exhaust gas leaving chiller in °F.
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